Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $43.58   6.592%   $46.4528   $46.45   $46.45   $46.50  
  Purchase #2 $224.39   4.861%   $235.2976   $235.30   $235.30   $235.30  
  Purchase #3 $89.68   4.637%   $93.8385   $93.84   $93.85   $93.80  
  Purchase #4 $129.71   13.603%   $147.3545   $147.35   $147.35   $147.40  
  Purchase #5 $165.26   4.197%   $172.196   $172.20   $172.20   $172.20  
  Purchase #6 $206.54   11.389%   $230.0628   $230.06   $230.05   $230.10  
  Purchase #7 $170.57   6.673%   $181.9521   $181.95   $181.95   $182.00  
  7 purchase totals = $1,029.73       $1,107.1543   $1,107.15   $1,107.15   $1,107.30